You have the service manual, right? I'm looking at the service manual
DVD for the 2002 Explorer (I saw you have a 2003).
In section 412-00; subsection denoted Diagnosis and Testing, Climate
Control System; there is a lot of verbage on how to execute the
selftest and retrieve various codes using only button press combos and
codes on the DATC display. There is also a diagnostic trouble code
chart, and directions to the pinpoint tests.
Read this stuff carefully, as I don't know what the effect on a 2003
(or a 2002 for that matter) might be.